The invention described herein relates to non-hygroscopic salts of L-carnitine and lower alkanoyl L-carnitines which lend themselves favorably to the preparation of solid compositions suitable for oral administration. The invention also relates to the compositions thus obtained.
It is well known that L-carnitine and its derivatives lend themselves to various therapeutic uses. For example, carnitine is used in the cardiovascular field for the treatment of acute and chronic myocardial ischaemia, angina pectoris, heart failure and arrhythmias.
In the nephrological field, L-carnitine is administered to chronic uraemic patients undergoing regular haermodialytic treatment to combat muscular asthenia and the occurrence of muscle cramps.
Other therapeutic uses have to do with normalisation of the HDL:LDL-VLDL ratio and total parenteral nutrition.
It is also well known that the salts of carnitine and its alkanoyl derivatives present the same therapeutic or nutritional activities as the so-called xe2x80x9cinner saltsxe2x80x9d and that they can therefore be used in their stead, provided the salts are xe2x80x9cpharmacologically acceptablexe2x80x9d, i e. they do not present toxic side effects.
In practice, then, the choice between the xe2x80x9cinner saltxe2x80x9d or a true salt of L-carnitine or alkanoyl L-carnitine depends more on which compound is more easily and economically available and on The European Patent Application EP 0 167 115 describes a novel derivatives of L-carnitine or of acyl L-carnitines or esters thereof, obtained by salfication with suitable acids or acidic aminoacids, monosalifed with potassium ion, and pamoic acid belongs to the mentioned acids groups. U.S. Pat. No. 4,602,039 describes a novel L-carnitine or alkanoyl L-carnitine salts with a suitable acid, and among the listed acid pamoic acid is not mentioned. considerations of pharmaceutical technology rather than on considerations of therapeutic or nutritional activity.
It should therefore be clearly understood that, as far as the invention described herein is concerned, the usefulness of the above-mentioned salts does not consist in their different therapeutic or nutritional activity from those of known compounds but in their non-hygroscopicity vis-a-vis the corresponding internal salts.
Their non-hygroscopicity allows them to be easily processed, particularly with a view to the preparation of solid oral administration forms.
As is well known to experts in pharmaceutical technology, the processing of hygroscopic products entails the use of controlled-humidity chambers both for storage and for processing. Moreover, the finished product must be packaged in hermetically sealed blister packs to avoid the unwanted consequences of humidity.
All this entails greater costs both of storage of raw materials and of processing and packaging of the products.
Among the populations of the industrialised countries there is an increasingly widespread use of food supplements or xe2x80x9cnutraceuticalsxe2x80x9d both by sportsmen (amateurs or professionals) and by people enjoying good health.
The former use L-carnitine or food supplements containing carnitine because it favours the oxidation of fatty acids and provides the skeletal muscles with a greater amount of energy, thus enhancing performance and giving rise to less build-up of lactic acid in the muscles.
People enjoying good health use these food supplements as health foods, i.e. for the purposes of preventing diseases related to disorders of lipid metabolism.
It has been estimated that the amount of L-carnitine and its derivatives sold for non-ethical purposes is twice that sold for ethical purposes.
The US market for food supplements or nutraceuticals amounts to approximately 250 billion dollars, while in Europe a market worth approximately 500 billion dollars has been estimated (Food Labeling News, 1994, xe2x80x9cNutraceuticals market said to be a vast one, March, Vol. 2, No 25; King Communications Group Inc., 1993. xe2x80x9cNutraceuticalsxe2x80x9d Foods. Drink in Global market, Food and Drink Daily, April, Vol. 3, No. 503).
A number of non-hygroscopic salts of L-carnitine are already known.
For example, European Patent 0 434 88, (Lonza), filed on Dec. 12, 1990, describes the use of a non-hygroscopic salt of L-carnitine with L-(+)-tartaric acid. (salt already described, moreover, by Mxc3xcler and Strack in Hoppe-Seyler""s Z. Physiol. Chem., 353, 618-622, April 1972) for the preparation of solid oral administrations forms.
These salts, however, present certain drawbacks, such as, for instance, the release of trimethylamine after prolonged storage, which gives rise to an unpleasant olfactory effect due to the characteristic fishy odour of this amine. Furthermore, L-(+)-tartaric acid is not capable of forming non-hygroscopic salts with the lower alkanoyl L-carnitines, such as, for instance, acetyl L-carnitine.
The purpose of the invention described herein is to provide new non-hygroscopic salts both of L-carnitine and the lower alkanoyl L-carnitines. These compounds are the salts with pamoic acid with the following general formula: 
where:
R is hydrogen or a lower alkanoyl, linear or branched, with 2-6 carbon atoms;
if X=1, Yxe2x95x90COOH; and
if X=2, Yxe2x95x90COOxe2x80x94
Those salts are preferred in which R is selected from the group consisting of acetyl, propionyl, butyryl, valeryl and isovaleryl.
The salts of L-carnitine and the lower alkanoyl L-carnitines according to the invention are not hygroscopic and are extremely stable on storage.
The pamoates are pharmacologically acceptable salts approved by the Food and Drug Administration (FDA), as results, for example, from Int. J. Pharm., 33 (1986), 201-217.
Unlike the known salts of L-carnitine and alkanoyl L-carnitines, which are all hydrosoluble, the pamoates according to the invention are compounds endowed with poor hydrosolubility.
This property can be used to advantage to produce compositions with slow-release (or controlled release) of the active ingredient consisting in L-carnitine or one of its alkanoyl derivatives for the purposes of improving its absorption and prolonging the period of time during which blood levels of the compound are suitable for exerting the desired therapeutic or nutritional effect.
It is well known, in fact, that L-carnitine is a highly hydrosoluble compound and that it is rapidly excreted via the kidneys. Therefore, the administration of L-carnitine ensures adequate blood levels of the compound over too short a period for it to be able to perform for example, a protective function on the myocardium after myocardial ischaemia.
The subject matter of the invention described herein therefore also covers pharmaceutical, dietetic or nutritional compositions which produce slow, controlled release of L-carnitine or of its alkanoyl derivative.
If one desires to achieve high blood levels of L-carnitine or its alkanoyl derivative within a relatively short space of time and then maintain such optimal blood levels for a prolonged time period, according to the invention described herein one can use a composition consisting of a mixture of L-carnitine and/or alkanoyl L-carnitine in the form of a highly hydrosoluble salt, e.g. inner salt or hydrochloride, which makes all the L-carnitine or alkanoyl L-carnitine present in the composition immediately available, and one or more pamoates according to the invention, which, by slowly releasing the active ingredient, maintain substantially constant blood levels of this ingredient over a protracted period.
The invention described herein therefore also comprises a composition suitable for covering the daily requirement of L-carnitine and/or an alkanoyl L-carnitine, in which the alkanoyl has 2-6 carbon atoms, in an individual requiring such treatment, containing said L-carnitine and/or alkanoyl L-carnitine partly (a) in a free, immediately available form and partly (b) in a form ensuring its controlled release, characterised in that the ingredient (a) contains L-carnitine or alkanoyl L-carnitine in the form of inner salts or pharmacologically acceptable hydrosoluble salts; and ingredient (b) contains a salt of L-carnitine or alkanoyl L-carnitine with pamoic acid with general formula (I).